I used the N with the 1.4x and 400mm and it is a great combo. Used it 80% in that config on my last Africa trip and IQ and AF speed was excellent. At that price you can't really lose.
..... and I bought that very same 1D Mk2N from Condyk a few months ago and it is as good as he says! 
It complements my 5D (soon to be a 5D Mk2!
) perfectly. I use the 5D for landscapes, anything moving gets the 1D. In low light the 5D has a slight edge but I got some excellent indoor classical music shots using the 1D 2N with a 70-200 f2.8 IS L. Just don't expect much from ISO above about 1250.
, while a 1D Classic or XXD series would just feel inferior to the 5D.

